Idle vent valve



Jan. 6, 1959 c. E. WING 2,867,423

, IDLE VENT VALVE Filed April 2a, 1956 INVENTOR CHARLES E. WING ATTORNEY 'IDLE V'ENT VALVE Charles-EQWingEast LansingjMic h assignor to General 'Motors Corporation, Dtroit, iDelaware Application April .23, 1956,. SerialTNo. 579,807

*1 Claim. (Gi.- 261-'43) Mich, corporation of The present invention relates to an improved 'fuel reservoir venting mechanism for a carburetor. The present invention more specifically relates (to an improvement which makes cold starting easier withcarburetors'utilizing Such venting mechanisms are .shown in icopending appli- :cations Serial No..264,.l36.0lson.etalyfiled December 29,

1951 and Serial No. 579,806, filed April 23, 1956 Olson. While these mechanisms do greatly reduce hot starting problems, it has been found that under certain atmospheric conditions that a cold starting problem arises which the present invention seeks to alleviate.

With the fuel reservoir vent open, as is the case with the engine stopped, and further with the vehicle facing into a wind, it has been found that over a period of time the fuel in the reservoir will be evaporated through the fuel bowl vent to such an extent that cold starting of the engine becomes rather difficult.

It has been found that where the ambient air blows over the vent mechanism over a period of time, as might occur when a car was parked outside over-night, the fuel level in the bowl will be reduced to such an extent that the engine cranking time is perceptibly increased, e. g., to 9-12 seconds, until the fuel bowl level is sufficiently raised to supply an adequate starting charger This situation is particularly aggravated in cold weather when very rich starting mixtures are necessary.

It has been found that the evaporation of fuel from the reservoir is greatly accelerated as the velocity of the ambient air passing over the vent mechanism increases. It is theorized that the increased rate of evaporation is due to an aspirating action created by the air flowing rapidly over the reservoir vent. The aspirating action tends to reduce the pressure within the reservoir below atmospheric which, of course, accelerates the rate of surface evaporation.

Accordingly, it is a primary purpose of the present invention to reduce the evaporation of fuel when the fuel bowl or reservoir is vented to atmosphere. Pursuant to this purpose a device has been developed which in conjunction with venting mechanisms insures that the reservoir will be maintained at least at atmospheric pressure even when the ambient air is moving at a considerable velocity over the vent mechanism.

A preferred form of the mechanism by which the above purpose is achieved is shown in accompanying drawings and will hereinafter be described in detail.

In the drawings:

Figure 1 is a partially sectioned elevational view of a carburetor embodying the subject invention.

Figure 2 is a fragmentary plan view of Figure 1.

United States Patent .fuel free portion of the fuel reservoir.

2,867,423 Patented Jan. 6, 1959 Figure 3 is a fragmentaryenlargement of the ventmechanism embodying the subject invention.

Referring to Figure 1, acarburetor is zshown'rgenerally at and .includes a fuel bowl .or reservoir .casing 12, a

.throt tle'body 14and-a reservoir .cover16. Mounted .on

a :shaft 18 in the throttle body is a throttle valve .20, shown in a substantially closed.position. Also'fixed to the throttle shaft 18 is alever 22 articulatedatone end .to a throttle zpedal controlled rod -24. Likewise .to the throttle shaft .18 and adapted to rotate therewith :is .another-lever26 to which is articulated to one end of .a control link 28.

As already referred to above, .ithas been found desirable to provide a-reservoir venting mechanism which 16 is provided with anupstandinghollow vent casing30 which'communicates at its lower end with the upper or The vent casing 30 is formed with horizontallyalinged openings .32 and .34'therethrough. Opening .34 has securelyfitted therein .an apertured cover -36 which is-adaptedto slidablysupport .a valve -mernber38. The val-remember .38 includes .-a stem-40 slida'bly supported :in the'cover 36 anda valve head 42 adapted to seat against and close opening 32 in the vent casing 30. A seat or retainer member 44 is mounted on the end of valve stem 40 exteriorly to the vent casing 30 and is adapted to support one end of a spring 46, the other end of which spring biases against cover 36 and thereby urges the valve stem and head to the left, as viewed in Figure l, to close port 32.

In order to open valve 38 by moving valve head 42.

away from the vent port 32, a lever 50 is centrally pivotably mounted on the fuel reservoir casing 16 through a stud 51. Lever 50 includes a pair of arms 52 and 54. The arm 54 is adapted to engage with valve stem 40 and upon rotation of the lever 50 control the movement of vent valve 38. Arm 52 of lever 50 is articulated to the other end of throttle control link 28.

An impact valve 60 is provided for the purpose of preventing liquid fuel from splashing out of the venting mechanism and is specifically described and claimed in copending application Serial No. 579,806, filed April 23. 1956 Olson.

In the vent mechanism as thus far described it will be seen that with the throttle valve 20 closed or substantially closed, the vent valve 38 is held in an open position thereby communicating the fuel reservoir to atmosphere. This will be the condition of the vent mechanism wheneven the throttle valve is in an idling or closed position as will be the case when the vehicle is stopped and the carburetor inoperative. As already noted, it is under this condition, as when the vehicle is parked over a reasonably long period of time, that excessive fuel bowl evaporation will take place particularly when the ambient air is moving over the carburetor at above normal velocities.

While the subject invention is not limited to a precise type of fuel reservoir venting mechanism, for illustrative purposes it has been shown in combination with a venting mechanism of the general type shown and described in copending applications Serial No.

:- 264,136 Olson et a1. filed December 29, 1951 and Serial thereby reduce the pressure within the fuel reservoir be- A low atmospheric and thus facilitate the surface evaporationof fuel within the reservoir. To avoid the occurrence of this phenomenon a shield 70 is mounted in any convenient manner upon the reservoir cover 16 so as to partially cover the vent casing 30.

The shield 70 is of a sufficient size to permit the vent valve 38 to open. It "will also be noted that in this embodiment of the invention, the opened end 72 of the cup-shaped shield 70 faces in an up-wind direction with respect to the normal air flow past the carburetor. In this respect the shield 70 opens in the opposite direction relative to vent port 32. This relationship between the shield and the vent port 32 has been found to eliminate 'the aspirating action otherwise occasioned by the rapid flow of air over the vent mechanism. With this arrange- "ment of the shield a static air pressure head will be built "up in the space confined between the shield and the vent mechanism 30 which will insure the pressure in the float bowl being-at least atmospheric. It is even likely that this static pressure head created by the ram-velocity-eifect of rapidly flowing ambient air would be slightly super atmospheric which would, of course, greatly reduce the surface evaporation of fuel from the fuel reservoir.

While the arrangement of the shield 70 with respect to {the vent casing 30 is preferred with theparticula'r car-buretor used for illustrative purposes, it is to be understood that the shield function may be achieved with various other structural arrangements. The important relationship between-the cover or shield and the associated vent 30 mechanism is that they be oriented with respect to air flow so as to avoid any aspirating action relative to the fuel bowl-"and even more preferably that the arrangement insure an atmospheric or super atmospheric static pressure head within the fuel bowl reservoir.

I claim: 1

A carburetor comprising a throttle valve, a fuel reservoir casing, a cover for said casing, a vent casing disposed on said cover and in communication with said fuel reservoir, a port insaid vent casing open to atmosphere, a vent valve normally closing said port, and means connecting said throttle and vent valves permitting said vent valve to open when said throttle valve is in a substantially closed position, and a cup-shaped shield mounted ,on said cover and partially surrounding said vent casing, said port opening downwind and said shield opening upwind with respect to the direction in Which ambient air normally passes over said carburetor, said vent valve opening toward the closed end of said shield.

References Cited in the fileof this patent UNITED STATES PATENTS 1,817,860 Wahnish Aug. 4, 1931 2,013,787 Moseley Sept. 10, 1935 2,201,603 Wirth May 21, 1940 2,316,882 Moseley et a1 l Apr. 20, 1943 I FOREIGN PATENTS 113,434 Great Britain Jan. 15, 1919 1,087,311 France Aug. 25, 1954 Great Britain Mar. 14, 1956 

